The invention concerns an electronic vehicle dynamics regulation system for a land vehicle, which system is set up at least for intervention on steering and brakes. Such systems make it possible to provide numerous functions such as are not possible with today's systems with integrated brake and engine intervention (e.g. yawing moment compensation for braking on μsplit).
The steering intervention by the vehicle dynamics regulation system can act on both power steering systems, in which the steering force is applied exclusively from an energy source which is present in the vehicle, and power-assisted steering systems, in which the steering force is applied by the driver and from an energy source which is present in the vehicle. In the case of overlaid steering, depending on steering wheel movements which the driver controls and the current vehicle-dynamic magnitudes of the vehicle, an additional steering angle is actively set via servo motors. The additional steering angle is usually overlaid on the steering wheel movements which the driver controls via a planetary gear train. It is thus possible to implement driver assistance functions (e.g. variable steering support depending on the vehicle speed) or stabilisation functions (e.g. improving driving stability, side wind compensation, counter-steering on a non-homogeneous surface, etc.). A possible implementation of such a steering intervention system is described in, for instance, ATZ Automobiltechnische Zeitschrift (automotive engineering journal) 100 (1998) 9, “Die Servoelectric von ZF (ZF's Servoelectric)”.
The braking intervention can take place by means of braking equipment which can build up braking forces independently of or in addition to the driver. This is possible, for instance, by means of a hydraulic braking system which has anti-lock system, drive slip regulation and/or electronic stability programme functions. Such braking systems are capable of and intended for automatic braking. This is understood to include braking processes which usually take place independently of any force which the driver has applied to the pedal. These are, for instance, drive slip regulation, which prevents wheelspin of individual wheels during starting by targeted braking, or vehicle dynamics regulation (electronic stability programme, ESP), which adapts the vehicle behavior at the limit to the driver's wishes and road surface conditions by targeted braking of individual wheels, or adaptive cruise control, which among other things maintains a preset distance of the driver's own vehicle from the vehicle in front by automatic braking.
The sensor signals (which the vehicle dynamics regulation system processes) are prepared, the vehicle-dynamic setpoint magnitudes are calculated, and the manipulated magnitudes in each case are specified, usually by each of the regulation systems separately, on separate controllers. From the requirements-which are determined in this way, information is then generated and exchanged between the individual regulation systems. For instance, to calculate the setpoint vehicle movement magnitudes, ESP requires information about the total steering angle and the actually existing wheel steering angle. Compared with previous ESP systems, modifications to the ESP algorithms are unnecessary to a large extent. The vehicle's safety-critical range is reached when the braking pressure exceeds about 20 bar.
With the electronic vehicle dynamics regulation systems described above, it is possible to implement active steering. To a larger extent than with convenience influencing of steering processes, into the vehicle's safety-critical range, steering wheel movements which the driver controls are overlaid or replaced by a steering force which is applied by a motor. The vehicle's safety-critical range is reached when the steering moment to be overlaid by the steering wheel movement which the driver controls exceeds about 3 Nm, or when the steering angle to be overlaid exceeds about 0.4°.
With both previous and today's systems, for safety reasons, redundant provision of the yaw angular velocity and transverse acceleration sensors is seen as indispensable. This applies in particular to systems which are capable of generating relatively large steering moments or angles to be overlaid, with high dynamics. These sensors, which are present at least twice, are at least partly present separately for each of the vehicle dynamics regulation system or its regulating unit, and the braking systems of the anti-lock system, drive slip regulation and the electronic stability programme. Their signals are captured and evaluated separately. As part of a plausibility check on the signals, the measurement results are exchanged and compared between the individual systems or their regulating units. If there is a significant difference, the systems can detect an error case and be brought into a safe state.